Certain installations for placing ships high and dry or in the water comprise an elevator intended for raising each ship from the water up to the level of the ground. Such an elevator comprises a platform raised by winches. The boat rests on the platform during transport from the water upto the level of the ground, that is to say, upto the position where it emerges. Each boat must then be moved horizontally from the elevator over to a docking position.
Horizontal transport of a ship is generally carried out by means of wheeled trolleys located under the keel of this ship. This mode of transport lacks flexibility for absorbing the unevenesses in the ground and for spreading the load of the ship. Furthermore these trolleys serve only one direction, which limits the number of boats which can be docked over a given area.
In order to avoid this disadvantage an installation has been designed for transport by trolleys, which enables the boat to be moved along any horizontal direction. In this installation the boat rests upon a set of beams arranged perpendicularly to its longitudinal axis. Generally the boat rests upon each beam by a central chock and side chocks for shoring-up. Each beam rests at its ends upon two trolleys which run each upon one two-railed track. The different trolleys are arranged along two lines and each portion of the boat is supported by way of the beam and the trolleys upon four rails, which ensures good distribution of the loads. The beams are connected together by cross-bars. The bearing of each beam upon each trolley is effected by way of a hydraulic jack. This hydraulic jack is double-acting.
The jacks, when the beams are bearing on the ground, enable the trolleys to be raised above the rail and thus to swivel from one track to another track. Hence changes in direction may be achieved. The jacks above all enable the boat to be supported elastically and isostatically with respect to the ground. The jacks supporting the beams are distributed in three groups. All of the jacks of one and the same group are connected together so that the reactions from these jacks are equal. A first group comprises the jacks associated with one fractional part of the trolleys from the line of trolleys running upon one of the tracks. The second group comprises the jacks associated with one fractional part of the trolleys from the line of trolleys running on the other track. The third group groups together the jacks associated with the trolleys located at one end of each line and running upon the two parallel tracks. Each group of jacks is equivalent to an imaginary support at the centre of the geometrical figure which they define. The three resultants due to the three groups of jacks are located at the corners of an isosceles triangle the main height of which is parellel with the longitudinal axis of the boat.
In certain installations the side chocks for shoring-up bear against the beams by way of jacks. These jacks enable the shoring chocks to be adjusted for height as a function of the boat to be supported. The balancing of the loads between the different chocks is in spite of all that imperfect. The shoring-up must be achieved by trial and error and necessitates manual interventions. Apart from this disadvantage concerning the shoring-up, these known installations do not enable ships to be supported which are of heavy tonnage and great width.